Abstract

The isolation of integral surface membrane molecules participating in adhesive phenomena is an important but elusive goal of developmental and cell biology. Adhesion-inhibiting polyclonal antibodies were first used by Gerisch (1977) to identify glycoproteins responsible for Dictyostelium aggregation. This immunological approach has been used subsequently by several groups for the study of cell-cell and cell-substratum adhesion in mammalian systems. In this paradigm, a broad-spectrum polyclonal antiserum is raised that interferes with the adhesion process. Relevant cell surface molecules are then detected and subsequently purified by monitoring their ability to block antibody-induced alterations in adhesion. This approach has resulted in the identification and isolation of membrane glycoproteins involved in adhesive phenomena in several systems (Thiery et al., 1977; Bertolotti et al., 1980; Edelman, 1983; Damsky et al., 1981, 1983; Knudsen et al., 1981; Kemler et al., 1977; Johnson et al., 1979; Ducibella, 1980; Takiechi et al., 1981; Hyafil et al., 1981). Although this approach has been fruitful, it has limitations. First, with a broad-spectrum serum that perturbs adhesion, it is not possible to use affinity chromatography to purify the antigen. Therefore purification schemes must be developed using an antiserum inhibition assay to monitor progress. Second, if more than one polypeptide is present in the purified blocking activity, the relation of each to adhesion must be established.